That which primarily characterizes annular saws is that they lack a central shaft as a result of which the sawing depth is greater than the radius of the circle. Portable sawing machines have therefore been able to be developed for sawing up to a sawing depth of about 30 cm. The annular saw has therefore involved a novel idea when it is a question of mobile cross-cutting saws for qualified applications. Examples of use are in fire protection for sawing through roofs, walls and floors regardless of whether there are nails or other iron objects; sawing into motor-car bodies and other sheet-metal and iron constructions; sawing concrete pipes, sawing up asphalt, making holes in concrete and lightweight concrete walls and so on.
A problem which is encountered when sawing in objects and materials of the above mentioned kind has to do with the extensive generation of heat. Another problem concerns the removal of saw dust and other particles from the kerf produced by the saw blade. These problems may arise also for conventional circular saws but they are pronounced in the present field not only because of the heavy duty of the saw but also of the fact that the kerf may be made deeper than by conventional circular saws of the same dimensions and therefore not readily accessible for introduction of fluids by conventional means.